Note: This was written for Open Philanthropy’s Cause Exploration Prize, in response to their prompt for important pollution in low and middle-income countries. Don't be intimidated by the reading time - 32% of it is due to the reference list, and 24% is optional footnotes.

Summary

  • Developmental neurotoxicants (DNTs) are chemicals that have an adverse effect on the structure or function of the nervous system due to early-life exposure. Open Philanthropy is aware of lead as an exemplar DNT. I argue Open Phil should target other DNTs that are widespread, potent, neglected, and tractable.
  • The weight of evidence suggests prenatal exposure to organophosphate pesticides is associated with a decrease in the IQ of children. Large numbers of pregnant women in low and middle-income countries may have sufficient organophosphate exposure to produce cognitive deficits in their children. Banning some or all organophosphate pesticides in low-and-middle-income countries could reduce the loss of IQ and so improve wellbeing, and appears cost-effective.
  • Accelerating testing to identify unknown developmental neurotoxicants is speculative, but could confer significant value cost-effectively.
  • Mercury, polybrominated diphenyl ethers, and arsenic all have fertile research questions that could direct action.

Acknowledgements

Thanks to Dr. Peter Morris, Clare Donaldson, Judith Rensing, Sam Hilton, and Tony Senanayake for helpful comments, advice, and encouragement, though all errors are my own. Thanks especially to Bailey Coleman, Dr. Megan McHenry, and their team for early access to their draft of “Pesticides and neurodevelopment of children in low and middle-income countries: a systematic review”.

Introduction

Developmental neurotoxicants (DNTs) are chemicals with an adverse effect on the structure or function of the nervous system due to early-life exposure.[1] Because they affect lifelong IQ and thus lifetime earnings, DNTs have cost trillions in value globally.[2] Lead is an important example, which Open Philanthropy is already aware of. I claim Open Phil should expand to work on other DNTs that are widespread, potent, neglected, and tractable.

I focus here on organophosphate pesticides. I also analyse increased effort to find unknown DNTs. I end with key research questions for mercury, polybrominated diphenyl ethers (PBDEs), and arsenic.

Organophosphate pesticides

Organophosphates are a common class of pesticide used mainly as agricultural insecticides (see Wikipedia). Humans become exposed via eating pesticide-treated food, hand-to-mouth behaviour from contaminated surfaces, breathing airborne residues, and skin absorption.[3]

Some high-income countries (HICs) have been restricting organophosphates since 2001, with greater momentum recently.[4] Regulation on pollution to protect health in low and middle-income countries (LMICs) has often lagged HICs by decades or more.[5] I argue we should not let such a lag happen again, but instead accelerate the arrival of regulation of organophosphates for agricultural use in LMICs.

Pesticide bans on suicide-prevention grounds appear to have not affected agricultural yield, and organophosphates are said to have accessible alternatives.[6] However, pesticide restrictions may have reduced agricultural yield in the past, and individuals in target LMICs may have strong views on whether restrictions are justified. Estimating the potential impact of bans on agricultural yield and livelihoods would be an important component of fuller analysis.

I claim that banning some or all organophosphate pesticides in some LMICs would cause a slight increase in the IQ of a significant number of those countries’ children. I argue the claim in three parts. I then assess importance, neglectedness, and tractability. I perform back-of-the-envelope calculations for three candidate countries, and discuss uncertainties.

The argument

Sufficient prenatal exposure to organophosphate pesticides is associated with the loss of IQ in children

Animal evidence

The unifying mechanism of organophosphates is the inhibition of acetylcholinesterase (AChE), which breaks down the neurotransmitter acetylcholine. This mechanism was the basis for early studies attempting to establish safe organophosphate levels in humans.[7] However, animal and in vitro models support developmental neurotoxicity of some organophosphates at doses below the threshold of AChE inhibition.[8] Animal and in vitro models have suggested a surfeit of other mechanisms for the developmental neurotoxicity of organophosphates:[9]

Human evidence

Epidemiological evidence

Three cohort studies in the U.S. form the foundation of epidemiological evidence.[10]

Rauh et al. (2011) measured levels of a common organophosphate called chlorpyrifos in the umbilical cord blood plasma in 265 children in New York City.[11] They tested the children at age 7 and found that each standard deviation increase in chlorpyrifos exposure was associated with a 1.4% decrease in full-scale IQ (FSIQ) (0.94-1.8 points, p = 0.048) and 2.8% decrease in working memory (1.6-3.7 points, p = 0.003), with no interaction between this effect and any of the demographic variables or measures of other chemical exposures.

Organophosphates break down into metabolites called dialkyl phosphates (DAPs), which can be measured in urine as a marker of organophosphate exposure. Bouchard et al. (2011) measured DAPs in pregnancy and then tested the resulting 329 children at age 7.[12] They found that each 10-fold increase in prenatal DAP was associated with a loss of 5.3 points on FSIQ (-8.6 to -2.0, p = 0.01), significant for all subcomponents (working memory, processing speed, verbal comprehension, perceptual reasoning). Rowe et al. (2016) re-assessed the same cohort at age 10, but measured exposure using the California Pesticide Use Reporting system.[13] The independent difference between the highest and lowest quintile of prenatal proximal pesticide use was a deficit of 4 IQ points.

Engel et al. (2011) measured maternal DAPs and assessed 169 children at 6-9 years of age. They found decrements in FSIQ and other indices, but these effects were modest, imprecise, and specific to particular DAP subsets.

Bellinger (2012) weighted the two studies relating maternal urinary DAP to childhood FSIQ by sample size.[14] He suggests an effect size of -4.25 IQ points for a 10-fold increase in maternal urinary total DAP, with an assumption of no effect under 50 nmol/L and a ceiling of -4.25 points above 500 nmol/L.

According to the European Chemicals Agency, 28 additional epidemiological studies performed since 2017 are “in line with the remaining body of evidence but do not provide significant new information”.[15]

Systematic reviews

A 2019 systematic review concluded there was considerable evidence that organophosphate pesticides negatively affect neurodevelopment, while noting controversy.[16] 45/50 studies found an association. 22/24 studies (n = 6637) on school-aged children found a significant negative neurodevelopmental effect, with 14 studies being cohort-based.

This summary was concordant with three earlier systematic reviews.[17] In addition, Munoz-Quezada et al. 2013 looked at studies assessing dose-response relationships, and reported that 11/12 found a significant dose-response. 10 longitudinal studies based on 3 birth cohorts found prenatal organophosphate exposure had a dose-response relationship with cognitive deficits in children aged 7, behavioural deficits in toddlers, and motor deficits in neonates. The diversity of outcome measurements precluded Munoz-Quezada et al. from conducting a meta-analysis.

A meta-analysis by an Iranian group found a significant effect of prenatal occupational organophosphate exposure on children’s cognition (figure below), although it was based on only two studies after excluding a third.[18]

According to a draft of a systematic review to be published this year, 19/26 studies in LMICs found a significant negative effect between pesticide exposure and at least one neurodevelopmental domain.[19] Three questionnaire-based assessments of maternal exposure including organophosphates associated cognitive deficits with pesticide use in Tanzania and Ecuador.[20]

Other subsequent evidence

Below is a summary of other studies assessing neurocognitive effects of prenatal organophosphate exposure published after the most recent systematic review:

Indirect evidence

Ross et al. (2012) conducted a systematic review and meta-analysis of occupational studies assessing long-term, low-level exposure to organophosphates without acute intoxication in adults. They found 14 studies (n = 1600) and a significant association with impaired neurocognitive function.

Ramirez-Santana et al. (2020) assessed adults in Chile. They found that long-term exposure (>10 years) to organophosphate or carbamate pesticides without any acute intoxication predicted poorer neurobehavioral impairment in adults, with the effect increasing during the spraying season.

Expert opinion

Expert opinion bolsters the conclusion that organophosphates are likely DNTs.

The European Food Safety Authority concluded in 2019 that prenatal organophosphate exposure consistently produces cognitive and behavioural deficits.[21]

The U.S. EPA concluded in 2016 that epidemiological evidence was sufficient to conclude that chlorpyrifos was causing neurodevelopmental effects at concentrations below the level of AChE inhibition.[22]

An expert panel used a method from the Intergovernmental Panel on Climate Change, and suggested the probability range for a causal relationship between organophosphates and loss of IQ was 70-100%.[23] They rated the toxicological evidence ‘strong’ and the epidemiological evidence ‘moderate-high’.

A substantial number of pregnant women in some LMICs have significant exposure to organophosphate pesticides

Cognitive deficits from organophosphate exposure are likely significant in HICs.[24] LMICs tend to have a larger rural population, less regulation of pesticides, less-informed applicators, and more nutritional deficiencies (which exacerbate pesticide effects).[25]

In addition to diet, women living in agricultural areas can be exposed occupationally, para-occupationally, residentially, and through agricultural drift (e.g. windborne from application or residues on plants/soil).[26]

Data on organophosphate use

Incomplete data suggests that LMICs use a substantial amount of organophosphates, especially in Asia:[27]

Asia also dominates imports of hazardous pesticides:[28]

Import and usage data, farmer surveys, chemical analysis of markets, passive environmental sampling, and farmer-worn silicone wristbands all support substantial organophosphate use in Africa.[29]

A Pesticides Action Network report suggests hazardous pesticide use is widespread in Asian LMICs.[30]

Exposure in pregnant women in LMICs

Baumert et al. (2022) measured 6 serial urinary DAPs in 316 pregnant women in rural Thailand, and found higher levels than those in the U.S. cohort studies:

Kongtip et al. (2013) assessed 86 pregnant women in Thailand, only half of whom lived near farmland. They found DAP levels throughout pregnancy to be at least double the minimum assumed by Bellinger for an effect on IQ. Other studies in Thailand are consistent with this level.[31]

Samples of meconium (a baby’s first stool) in rural Thailand showed organophosphate exposure in 98% of cases.[32]

For pregnant women in rural Bangladesh, pesticide-specific biomarkers were 3-38X higher than US females.[33]

A study of 1303 pregnant women in China found ~11X higher median concentrations of a pesticide-specific biomarker compared to a U.S. survey.[34]

Exposure in other populations in LMICs

A recent comparison showed that exposure measured by DAPs in children in Thailand and Malaysia is comparable to HICs:[35]

This pattern is consistent with results from China, as well as a review of studies on child labourers in Egypt and Brazil.[36]

An eight-country comparison from 2006-2014 shows the following for three organophosphates (chlorpyrifos, parathion, and diazinon):[37]

Li & Kannan (2018) represent the proportion of the population experiencing a daily intake of chlorpyrifos above the hazardous limit:

While I cannot be confident of exhausting the literature, the majority of studies show LMICs to have an equal or greater exposure to organophosphates than the U.S. studies which suggested an effect on IQ.

Banning the problematic pesticides could reduce exposure

A critical piece of future evidence that Open Phil could pursue is a comparative study or randomised-controlled trial to assess whether controls on organophosphates lead to higher IQs in children, though the time this takes should be considered versus the value of information gained.[38] Whilst there isn’t direct evidence yet that pesticide bans lead to gains in IQ, there is evidence that bans of specific pesticides lead to lower exposure, described next.

The U.N. (2022) says that countries with strict regulations have reduced the effects of organophosphates, although their citations for this claim are about birds.

Food monitoring and human biomonitoring show an abrupt and significant decline in chlorpyrifos exposure following the EU ban in 2016.[39]Israeli data showed declining DAPs in pregnant women following restrictions of 18 organophosphate ingredients.[40]

The U.S. phased out chlorpyrifos and diazinon in 2000/01 for residential use. Decreases in exposure have been found in young children’s environment and urine, and prenatal personal air samples.[41] A NYC cohort found chlorpyrifos exposure halved over ten years, while markers of pesticides that were not banned did not change.[42]

Organochlorines are a class of pesticide that were banned in the 1970s. Despite being a more persistent class, Li et al. (2022) assess serum organochlorine levels in the U.S. and find declines of around 15% every 2 years. Comparing generations born before and after the bans suggest a drop of 40%.[43]

A systematic review which found that bans on pesticides reduced pesticide-suicides and overall mortality.[44] Data in Sri Lanka showed that bans on specific pesticides reduced their use in pesticide-suicides substantially.[45]

Importance

Gaylord et al. (2020) estimate that from 2001-2016 organophosphates were responsible for the loss of >26 million IQ points, which due to the expected loss in lifetime earnings results in a cost of around $735 billion, or $46B/year. Similarly, Attina et al. (2016) estimate that cognitive deficits due to organophosphates cost the U.S. $44.7B/year, or 0.3% of GDP.

Bellanger et al. (2015) estimate that organophosphate-caused cognitive deficits cost the E.U. $194B (sensitivity: $62B-$259B) annually, or 1.14% of GDP.[46]

The combined GDP of LMICs is $36.32 trillion.[47] If organophosphates were affecting LMICs to a similar extent as the U.S., the cost of organophosphates to LMICs would be $108B/year. If similar to the EU, the cost to LMICs would be $414B/year.

Given higher agricultural employment rates and rural population size, a relative lack of pesticide regulation, and unsafe pesticide practices, it would be reasonable to expect organophosphates to be an even larger problem for LMICs than for the U.S./E.U.

A more formal estimate of the cost to LMICs with quantified uncertainty is beyond the scope of this paper, though could be a useful project. Note that the above estimates are smaller than the annual cost of cognitive deficits caused by lead in LMICs (~$1 trillion), arrived at by similar methods and authors.

I quantify estimates of the ‘units of value’ lost due to the decline in IQ for three case studies in the BOTEC section.

Neglectedness

Political

According to the Lancet Commission, global response to pollution-caused ill-health since 2017 has been weak.[48]

The Strategic Approach to International Chemicals Management (SAICM) is the only comprehensive process targeting chemical pollution.[49] It intended to explore a global action plan on highly hazardous pesticides (HHPs) at its next 5-yearly conference in 2021, but that meeting has been postponed indefinitely.[50] There is no mechanism for the global action plan, and a government representative from Africa stated that “Most LMICs lack the knowledge and capacity to implement.”[51] Involvement in SAICM is voluntary, and its total 2022 budget was $5.9M.[52]

Even the labelling of hazardous substances has seen little activity, with no implementation commitments made in 1992 by 120 countries including all of Africa (except Zambia) and all of South Asia.[53]

The Global Environment Facility, a critical source of finances in environmental work, focuses almost exclusively on Persistent Organic Pollutant (POP) pesticides under the Stockholm Convention.[54] POPs are chemicals that are toxic, persist in the environment for years, and accumulate in food chains. Chlorpyrifos is being considered for inclusion, but most organophosphates are unlikely to be included in the near-term future.[55]

I found information for one BOTEC case, the Philippines, for the technical regulatory agency in charge of pesticides.[56] In 2023 its budget for regulation was $1.6M.[57]

Academic

83% of occupational exposure studies for pesticides occur in high or upper-middle income countries, with only 1.1% from low-income countries.[58] Key research gaps concern both developmental neurotoxicity and risks to pregnant/nursing women and young children.[59]

The Global Burden of Disease project only assesses factors with detailed data on both exposures and outcomes, and where there is strong evidence of causation.[60] As such, they do not include estimates of the global burden due to pesticides, let alone organophosphate pesticides.[61] However, the GBD authors note global exposure to pesticides would be important to include in the future, if data were available.[62]

Civil society

ToxicsLink is the South Asia coordinator for the International Pollutants Elimination Network ToxicsLink has total assets of ~US$539K, with their Chemicals focus area including lead, POPs, and mercury.[63]I’d guess less than $100K is spent on non-POP pesticides.

The Pesticide Action Network (PAN) appears to be the largest NGO group working on pesticides globally.[64] Their scientific grounding and risk of bias appears questionable, exemplified by their campaigns against genetically-modified organisms, or merging surveys with advocacy to participants. Combined, PAN’s global assets appear to be less than $4M.[65] I’d guess less than $1M is spent on LMIC regions.

The Center for Pesticide Suicide Prevention (CPSP) works with national governments in Asia and Africa to determine what pesticides are being used most in suicides, and then try to deregister them.[66] In 2021, GiveWell recommended a $7M grant from Open Philanthropy for CPSP’s costs for three years.[67] They appear well placed to work on reducing DNT pesticide exposure. However, despite overlap with their suicide-prevention work, tackling DNT pesticides would significantly alter CPSP’s activities in four ways:

  1. New pesticides: Targeting DNT pesticides would substantially add to the list of pesticides CPSP tries to deregister. CPSP list Sri Lanka, China and Bangladesh as countries that have significantly reduced their pesticide-suicide burden. Sri Lanka has only banned 11/41 organophosphates, China 16, and Bangladesh 5.[68] Thus reductions of pesticide-suicides do not always result in degregistration of organophosphates. 36.5% of organophosphates are not listed as HHPs, and only 18% of HHPs are organophosphates, suggesting that future HHP deregistrations will only partly reduce DNT burden.

  2. New countries:
    Cost-effectiveness of pesticide-suicide prevention drops as the burden of pesticide-suicide decreases.[69] Targeting DNT would lead to new countries becoming cost-effective targets for the CPSP, such as the Philippines and Nigeria.

  3. New advocacy tools:
    Tackling DNT would expand and strengthen arguments for specific pesticide deregistration, enhancing CPSP’s work with governments.

  4. New cost-effectiveness estimates:
    Tackling DNT would increase CPSP’s already impressive cost-effectiveness estimates, and make them more conceptually and empirically robust.

Tractability

One aspect of tractability concerns whether regulation targets single organophosphate pesticides or the whole class. Heterogeneity in the preclinical literature and DNT effects below the level of AChE-inhibition suggest the possibility that not all organophosphates are DNTs.[70] However, pesticide-specific evidence is limited by available data and a lack of specific exposure measures.[71]

Gunier et al. 2017 used California’s reporting system to estimate pesticide-specific effects, finding variable but large DNT effects for four separate organophosphates. 26/41 organophosphates are already considered highly hazardous (HHPs) by the FAO-WHO. Of the 15 non-HHP organophosphates, a cursory literature search found implications of developmental neurotoxicity for 9.[72] This evidence may be weak or wrong, but my impression is that a precautionary approach could justify a whole-class ban on organophosphate pesticides, and this has been recommended in the literature.[73]

A modest goal would be to regulate organophosphates in LMICs to the same degree as the E.U. and U.S. The current regulatory situation is summarised here.[74] 18/41 organophosphates have been withdrawn from registration in the U.S.; the E.U. has banned 26. Relevant LMIC precedent is set by China (16 banned) and Indonesia (21 banned). In my BOTEC cases, the Philippines has banned 2, and Bangladesh and Nigeria have both banned 5.

Targeted pesticide deregistrations have occurred in LMICs in the past, and GiveWell assesses the CPSP to have a good chance of success (30%-60%) in several Asian countries for deregistring pesticides on suicide-prevention grounds.[75]

There would be synergy between action on HHPs and DNT-relevant pesticides. The postponed SAICM conference will explore the execution of the Global Action Plan, while an alliance for HHP action is beginning to be designed.[76] The next 1-3 years could be pivotal to getting DNT on the agenda for global pesticide action.

While industry appears supportive of work on HHPs, they may be resistant to organophosphate regulation.[77] Assessing potential pushback/inertia would be an important part of a thorough assessment of this intervention.

Back of the envelope calculations

I conducted BOTECs for the Philippines, Bangladesh, and Nigeria, here. They should not be taken literally, but are illustrative of the area’s potential.

Inputs

Each section has an explanatory note in the spreadsheet. The section on organophosphate burdens is complicated, so its note is below.

Organophosphate burden

A comparator country with organophosphate exposure data is Thailand. Baumert et al. (2022) studied 330 pregnant women in two rural communities in northern Thailand, with the region chosen for generalisability to other LMICs. The table below shows results converted into nmol/L:

These figures are consistent with results from earlier, smaller studies in Thailand.[78]

Compared to Thailand, the Philippines is poorer, more rural, and imports more hazardous pesticides. Assuming their organophosphate burden is similar to Thailand is a conservative assumption.

Similar reasoning applies to Bangladesh. Pesticide-specific biomarkers in pregnant women in Bangladesh were many times higher than U.S. comparators.[79] Spotty data on organophosphate usage suggest broad comparability (such data is unavailable for Philippines/Nigeria):

Although both are trending down, the Baumert et al. (2022) samples (collected 2017-2019) suggest that significant exposure remains.

As further corroboration, the incidence of acute unintentional pesticide poisonings in agricultural populations may be a proxy of unsafe pesticide practices and prevalence of toxic pesticides. The incidence in Thailand is 36%, while the Philippines and Bangladesh are 57.99% and 55.64% respectively.[80]

Nigeria is the least certain case. Nigeria has a higher incidence of acute unintentional pesticide poisonings than both South Africa and Thailand.[81] Urinary DAPs in women in South Africa were substantially higher than the U.S. and E.U., and pesticide-specific biomarkers were higher than Bangladesh. A conservative assumption is that Nigeria’s organophosphate exposure is similar to Thailand/Bangladesh.

60 nmol/L is the level at which a 20% reduction (the highest reduction I consider) remains above the 50 nmol/L cut-off for a DNT in the literature. Based on a normal distribution on the Baumert data, ~70% of the rural population are above 60 nmol/L.

Results

For the Philippines, my conservative model suggests a $450,000 program regulating organophosphates could be 42X as cost-effective as GiveDirectly. Such a program would need to reduce exposure by 1.35% to still be at least 10X as cost-effective as GiveDirectly (a rough funding threshold). If the program reduced exposure by 4%, costs could be as high as $1.3M to still break the ‘10X bar’.

For Bangladesh, my conservative model suggests a $390,000 program would be 90X as cost-effective as GiveDirectly. Such a program would need to reduce exposure by 0.53% to break the 10X bar. It could cost $3.5M and still break the ‘10X bar’.

For Nigeria, my conservative model suggests a $450,000 program would be 66X as cost-effective as GiveDirectly. It would need to reduce exposure by 0.3%, or alternatively cost less than $3M, to still break the ‘10X bar’.

As well as the conservative case for each country, I also made a ‘best-guess’ scenario, seen in the table (open image in new tab due to formatting).

Limitations, reasons I’m wrong, and further questions

Two particularly important sets of limitations

Randomised-controlled trials for organophosphate exposure don’t exist yet. Current epidemiological evidence is limited by [82]:

  • limited power and precision

  • exposure to multiple neurotoxicants, which can confound or combine non-linearly

  • needing data on exposures in the prenatal period - DNTs may not persist in the environment long or have specific/reliable markers

  • needing data on long-term outcomes, which is expensive, difficult, heterogeneous between studies, and limits sample size.

Much evidence depends on using urinary DAPs, but these are an imperfect guide to organophosphate exposure as they [83]:

  • aren’t specific to parent pesticides

  • lack a dose-response relationship to clinical cholinergic signs/symptoms

  • have substantial intra- and inter-day variability

  • can have higher within-person than between-person variability [84]

  • have only partial correlation with measured organophosphate doses [85]

Seven good reasons to think I’m wrong

  • The estimated effect size is based on only 2 longitudinal studies, with a combined sample size of 498. While systematic reviews suggest the effect is supported by subsequent literature, the effect size has not been recalculated based on new data - and the true value may be significantly different.

  • The average expected IQ gains per child appears small on the BOTEC (partly due to adjustments for effect size, likelihood of effect being real, and modest assumptions of regulatory impact). The small differences become important because of the large populations affected. But it’s unclear if such small differences would be either detectable on neuropsychological testing or impactful for future earnings/wellbeing.

  • The agricultural impact of restricting organophosphates is probably bigger than HHPs - so the possible negative effects are higher and it may be more politically difficult (modelled in BOTEC as 40% adjustment, compared to a 70% adjustment used in GiveWell’s CPSP BOTEC).

  • The theory of change is long and uncertain. Here’s a simplistic linear schematic:
    funded intervention → bans/deregistrations → less organophosphate use → less organophosphate exposure in pregnant women → improved neurodevelopment of children → increased lifetime earnings → increased lifetime wellbeing.
    90% confidence in each arrow results in a conjunctive probability of 53%.[86]

  • A lot of work estimating the economic impact of developmental neurotoxicants uses similar methods and is conducted by similar groups of academics; this literature might be misguided or biased in particular ways, which this analysis doesn’t consider critically.

  • I use the GiveWell conversion of 0.22 units of value for each IQ point gained from their BOTEC for Pure Earth, and don’t interrogate it.[87] But this is a key part of estimating this intervention’s benefits, and could be questioned on normative and empirical grounds.[88]

  • While I have training in neuroscience and medicine, I am not a toxicologist, agriculturalist, or public health professional. I can’t be confident my summary of the literature is comprehensive.

Eleven questions

  • What is the expected loss of IQ points and earnings due to organophosphate pesticide exposure in LMICs?

  • Would regulation of organophosphates lead to higher child IQs in LMICs?

  • What is the expected impact of organophosphate restrictions on agricultural yield in LMICs?

  • How do the benefits of use of organophosphates for malaria control compare to potential DNT effects? Are there viable alternatives?

  • What is the contribution of other sources of organophosphate exposure, such as flame retardants?

  • Is there a DNT risk from other pesticide classes? [89]

  • How much would consideration of DNT change the CPSP’s activities?

  • What is the likely effect of HHP-focused activities on DNT burden?

  • What is the likely amount of industry resistance? How might it affect strategy?

  • What is the likelihood that chlorpyrifos is accepted as a persistent organic pollutant under the Stockholm Convention? What about other DNT-organophosphates?

  • What is the true relationship between neurodevelopmental outcomes measured in childhood and lifetime wellbeing?

Finding unknown developmental neurotoxicants

We need to be more proactive and systematic against DNTs. That might mean trying to find currently unknown DNTs. Here’s a speculative sketch of cost-effectiveness for that idea.

Global chemical production has increased 50X since 1950, and will triple again by 2050 relative to 2010.[90] There are around 350,000 unique chemicals or mixtures on the global market, of which 70,000 have been registered in the past decade.[91] Of these, nearly 30,000 have only been registered in developing countries.[92] The only comprehensive testing process is E.U.’s REACH.[93] Over ten years, REACH has assessed only 20% of end-products with production over 1 ton/year on the European market .[94] It appears likely that there are thousands of new chemicals being synthesised at high volumes in LMICs which will not be tested for developmental neurotoxicity for decades.

There are 201 known human neurotoxins, with around 2 added each year between 2006 and 2012; around half have high production volumes.[95] 11 are considered DNTs.[96] 5 DNTs are synthetic. Assuming independence, the chance of identifying a synthetic, high-production, developmental neurotoxicant within x years is:[97]
1 - (1 - (0.0248))^x

For 10 years, that chance is ≈22%.

For 20 years, ≈39%.

For 30 years, ≈53%.

I made a BOTEC for a program costing $10M/year for 20 years with the effect of accelerating DNT identification by 10 years[98]. Such a program could be >40X as cost-effective as GiveDirectly. It would need at least a 25% chance of accelerating detection by 10 years to clear the 10X bar. If we expected a 50% chance of 10-year accelerated detection, it could cost $20M/year - more than the operational expenditure of EU’s REACH[99] - for 20 years before dipping below the 10X bar. \

Is such an acceleration feasible? It took decades to recognise and restrict currently known synthetic DNTs.[100] If a synthetic DNT is first identified in 30 years time, it is probably being produced today. Instead of waiting 30 years to identify it, we could accelerate DNT identification compared to the historic record and our current trajectory, given REACH’s limited pace and focus on the European market.[101] We could leverage new toxicological techniques to scale DNT testing without commensurate increases in animal testing.[102] We could increase biomonitoring for developmental neurotoxicity in LMICs and better characterise DNT burdens.[103] We could act faster and more comprehensively when developmental neurotoxicity is suspected. We could prevent history from repeating itself.

This idea requires a much more detailed analysis, but I hope this sketch has suggested that it merits one.

Other developmental neurotoxicants

Space precludes detail on other DNTs, but here are some actionable questions:

  • Mercury is a global problem, and a key source is artisanal and small-scale gold mining.[104] However, there are large programs addressing this already.[105] Are there neglected, cost-effective opportunities in the space?

  • PBDEs cause a significant DNT burden, but are already covered by the Stockholm Convention.[106] Are there non-regulatory interventions that are scalable and cost-effective for reducing PBDE exposure in LMICs?

  • Arsenic’s global harms may be comparable to lead, but there’s a severe lack of data on global exposure and impact.[106:1] What’s the best estimate of arsenic’s DALY impact? What research is needed? What interventions are feasible?

Conclusion

Developmental neurotoxicants show potential as a focus for Open Philanthropy’s ambition to tackle the most important pollution in LMICs. Lead is an important example with work already being funded. Prenatal exposure to organophosphate pesticides likely decreases the IQ of millions of children in LMICs - accelerating the arrival of regulation could cost-effectively and seems neglected and tractable. Accelerating testing to find currently unknown DNTs earlier is a more speculative intervention, but appears promising. Mercury, PBDEs, and arsenic all have action-guiding research questions which appear fertile for future work.

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Stockholm Convention, 2022. “Chemicals proposed for listing under the Convention” Accessed here: http://chm.pops.int/TheConvention/ThePOPs/ChemicalsProposedforListing/tabid/2510/Default.aspx

Sudakin, Daniel L., and David L. Stone. 2011. "Dialkyl Phosphates As Biomarkers Of Organophosphates: The Current Divide Between Epidemiology And Clinical Toxicology". Clinical Toxicology 49 (9): 771-781. doi:10.3109/15563650.2011.624101.

​​Suwannakul, Boonsita, Ratana Sapbamrer, Natrujee Wiwattanadittakul, and Surat Hongsibsong. 2021. "Organophosphate Pesticide Exposures In Early And Late Pregnancy Influence Different Aspects Of Infant Developmental Performance". Toxics 9 (5): 99. doi:10.3390/toxics9050099.

Tarazona, Jose V., Maria del Carmen González-Caballero, Mercedes de Alba-Gonzalez, Susana Pedraza-Diaz, Ana Cañas, Noelia Dominguez-Morueco, and Marta Esteban-López et al. 2022. "Improving The Risk Assessment Of Pesticides Through The Integration Of Human Biomonitoring And Food Monitoring Data: A Case Study For Chlorpyrifos". Toxics 10 (6): 313. doi:10.3390/toxics10060313.

Thistle, Jake E., Amanda Ramos, Kyle R. Roell, Giehae Choi, Cherrel K. Manley, Amber M. Hall, and Gro D. Villanger et al. 2022. "Prenatal Organophosphorus Pesticide Exposure And Executive Function In Preschool-Aged Children In The Norwegian Mother, Father And Child Cohort Study (Moba)". Environmental Research 212: 113555. doi:10.1016/j.envres.2022.113555.

Todd, Spencer W., Eric W. Lumsden, Yasco Aracava, Jacek Mamczarz, Edson X. Albuquerque, and Edna F.R. Pereira. 2020. "Gestational Exposures To Organophosphorus Insecticides: From Acute Poisoning To Developmental Neurotoxicity". Neuropharmacology 180: 108271. doi:10.1016/j.neuropharm.2020.108271.

ToxicsLink, 2019. “2018-2019 Annual Report”. Accessed here: http://toxicslink.org/docs/Toxics%20Link%20-%20Annual%20Report%202018-19%20final.pdf

UN Environment Programme, 2019. “Global chemicals outlook II: from legacies to innovative solutions: implementing the 2030 Agenda for Sustainable Development.” Geneva: United Nations Environment Programme. Accessed here: https://www.unenvironment.org/explore-topics/chemicals-waste/what-we-do/policy-and-governance/globalchemicals-outlook

United Nations Environment Program, 2020. “2020 Update on the Global Status of Legal Limits on Lead in Paint”. Accessed here: https://www.unep.org/resources/report/2020-update-global-status-legal-limits-lead-paint

United Nations, 2022. “Synthesis Report on the Environmental and Health Impacts of Pesticides and Fertilizers and Ways to Minimize Them: Envisioning a Chemical-safe World” Accessed here: https://wedocs.unep.org/handle/20.500.11822/38409

van den Dries, Michiel A., Sander Lamballais, Hanan El Marroun, Anjoeka Pronk, Suzanne Spaan, Kelly K. Ferguson, Matthew P. Longnecker, Henning Tiemeier, and Mònica Guxens. 2020. "Prenatal Exposure To Organophosphate Pesticides And Brain Morphology And White Matter Microstructure In Preadolescents". Environmental Research 191: 110047. doi:10.1016/j.envres.2020.110047.

van den Dries, Michiel A., Kelly K. Ferguson, Alexander P. Keil, Anjoeka Pronk, Suzanne Spaan, Akhgar Ghassabian, and Susana Santos et al. 2021. "Prenatal Exposure To Nonpersistent Chemical Mixtures And Offspring IQ And Emotional And Behavioral Problems". Environmental Science & Technology 55 (24): 16502-16514. doi:10.1021/acs.est.1c04455.

Vasamsetti, Krishna, Bala Murali, Nam Seok Kim, Kyongmi Chon, and Hong-Hyun Park. 2020. "Developmental Toxic Effects Of Phosmet On Zebrafish (Danio Rerio) Embryos". The Korean Journal Of Pesticide Science 24 (4): 343-351. doi:10.7585/kjps.2020.24.4.343.

Voorhees, Jaymie R., Diane S. Rohlman, Pamela J. Lein, and Andrew A. Pieper. 2017. "Neurotoxicity In Preclinical Models Of Occupational Exposure To Organophosphorus Compounds". Frontiers In Neuroscience 10. doi:10.3389/fnins.2016.00590.

​​Weerasinghe, Manjula, Melissa Pearson, Flemming Konradsen, Suneth Agampodi, J. A. Sumith, Shaluka Jayamanne, S. M. H. M. K. Senanayake, Sandamali Rajapaksha, and Michael Eddleston. 2020. "Emerging Pesticides Responsible For Suicide In Rural Sri Lanka Following The 2008–2014 Pesticide Bans". BMC Public Health 20 (1). doi:10.1186/s12889-020-08871-7.

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​​World Bank, 2022. Accessed here: https://data.worldbank.org/country/XO

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  1. Henck & Morford, 2010, “Developmental Toxicology” ↩︎

  2. Grandjean & Bellanger 2017, "Calculation Of The Disease Burden Associated With Environmental Chemical Exposures: Application Of Toxicological Information In Health Economic Estimation" ↩︎

  3. CDC 2017, “Organophosphorus Insecticides: Dialkyl Phosphate Metabolites Factsheet” Available: https://www.cdc.gov/biomonitoring/OP-DPM_FactSheet.html ↩︎

  4. Recent call to ban all organophosphates in Hertz-Picciotto et al. 2018. "Organophosphate Exposures During Pregnancy And Child Neurodevelopment: Recommendations For Essential Policy Reforms"
    The current regulatory situation is summarised here: https://docs.google.com/spreadsheets/d/1lPPu_B3LU5lHZQmvJa1bK-ssjlJc2ez_yX-D_Wv5Ln8/edit#gid=0
    List made by selecting organophosphates as listed by Hertz-Picciotto et al. 2018 from PAN-International’s list of banned pesticides, last updated May 2022, available here: https://pan-international.org/pan-international-consolidated-list-of-banned-pesticides/
    Recent history of USEPA’s position (including political determinants) nicely summarised in global context here: https://theconversation.com/the-epa-is-banning-chlorpyrifos-a-pesticide-widely-used-on-food-crops-after-14-years-of-pressure-from-environmental-and-labor-groups-166485 ↩︎

  5. A key example of LMICs lagging HICs in regulation is lead. For lead in paint, see https://www.unep.org/resources/report/2020-update-global-status-legal-limits-lead-paint
    For lead in gasoline, see https://ourworldindata.org/leaded-gasoline-phase-out
    On the lag on regulation in agriculture for agriculture-dependent countries, see https://www.worldbank.org/en/news/press-release/2016/01/28/agribusiness-rules-lag-in-agriculture-dependent-countries ↩︎

  6. https://centrepsp.org/the-solution2 , Hertz-Picciotto et al. 2018 ↩︎

  7. Sheppard et al. 2020, “Flawed analysis of an intentional human dosing study and its impact on chlorpyrifos risk assessments” ↩︎

  8. ECHA 2022, pp 30-33 ↩︎

  9. Figure taken from Voorhees et al. 2017, "Neurotoxicity In Preclinical Models Of Occupational Exposure To Organophosphorus Compounds".
    Balaguer-Trias et al. (2022) also suggest the gut-brain axis as another potential pathway ("Impact Of Contaminants On Microbiota: Linking The Gut–Brain Axis With Neurotoxicity"). ↩︎

  10. Well summarised by ECHA 2022, pp. 33-35. Specific references:
    Columbia cohort - Rauh et al. 2011 "Seven-Year Neurodevelopmental Scores And Prenatal Exposure To Chlorpyrifos, A Common Agricultural Pesticide";
    Mount Sinai cohort - Engel et al. 2011 "Prenatal Exposure To Organophosphates, Paraoxonase 1, And Cognitive Development In Childhood";
    CHAMACOS cohort - Bouchard et al. 2011, "Prenatal Exposure To Organophosphate Pesticides And IQ In 7-Year-Old Children". ↩︎

  11. Rauh et al. 2011 ↩︎

  12. Bouchard et al. 2011, ↩︎

  13. Rowe et al. 2016, ​​ "Residential Proximity To Organophosphate And Carbamate Pesticide Use During Pregnancy, Poverty During Childhood, And Cognitive Functioning In 10-Year-Old Children" ↩︎

  14. Bellinger, 2012, "A Strategy For Comparing The Contributions Of Environmental Chemicals And Other Risk Factors To Neurodevelopment Of Children" ↩︎

  15. ECHA 2022, “Risk Profile on Chlorpyrifos” ↩︎

  16. Sapbamrer & Hongsibsong 2019, ​​"Effects Of Prenatal And Postnatal Exposure To Organophosphate Pesticides On Child Neurodevelopment In Different Age Groups: A Systematic Review" ↩︎

  17. Gonzalez-Alzaga et al. 2014 "A Systematic Review Of Neurodevelopmental Effects Of Prenatal And Postnatal Organophosphate Pesticide Exposure";
    Munoz-Wuezada et al. 2013, "Neurodevelopmental Effects In Children Associated With Exposure To Organophosphate Pesticides: A Systematic Review";
    Koureas et al. 2012, "Systematic Review Of Biomonitoring Studies To Determine The Association Between Exposure To Organophosphorus And Pyrethroid Insecticides And Human Health Outcomes" ↩︎

  18. Bemanalizadeh et al. 2022, "Parental Occupational Exposure And Neurodevelopmental Disorders In Offspring: A Systematic Review And Meta-Analysis"
    They excluded Andersen et al. 2015 (“Occupational pesticide exposure in early pregnancy associated with sex-specific neurobehavioral deficits in the children at school age”), which estimated prenatal exposure based on interviewing the mother and employer, and which found significant neurodevelopmental deficits in girls only. ↩︎

  19. Thanks to Bailey Coleman for access to the draft. Permission to contact the authors was given by the Cause Exploration Prize team.
    Coleman et al. 2022 “Pesticides and neurodevelopment of children in low and middle-income countries: a systematic review” (pre-publication draft manuscript - for access contact Benjamin Stewart to ascertain author permission) ↩︎

  20. Cited in Coleman et al. 2022:
    Handal et al. 2008 “Occupational Exposure to Pesticides During Pregnancy and Neurobehavioral Development of Infants and Toddlers”;
    Handal et al. 2007, “Neurobehavioral Development in Children With Potential Exposure to Pesticides.”;
    Chilipweli et al. 2021, “Maternal pesticide exposure and child neuro-development among smallholder tomato farmers in the southern corridor of Tanzania.” ↩︎

  21. ECHA 2022, pp. 34 ↩︎

  22. Hertz-Picciotto et al. 2018 ↩︎

  23. Bellanger et al. 2015, “Neurobehavioral deficits, diseases, and associated costs of exposure to endocrine-disrupting chemicals in the European Union.” ↩︎

  24. See Grandjean & Bellanger 2017 for summary.
    E.U. - Bellanger et al. 2015;
    U.S. - Attina et al. 2016 “Exposure to endocrine-disrupting chemicals in the USA: a population-based disease burden and cost analysis.”
    and Gaylord et al. 2020, "Trends In Neurodevelopmental Disability Burden Due To Early Life Chemical Exposure In The USA From 2001 To 2016: A Population-Based Disease Burden And Cost Analysis";
    Canada - Malits et al. 2022, "Exposure To Endocrine Disrupting Chemicals In Canada: Population-Based Estimates Of Disease Burden And Economic Costs". ↩︎

  25. Coleman et al. 2022 (pre-publication draft), citing: Handford et al. 2015 (“​​A review of the global pesticide legislation and the scale of challenge in reaching the global harmonization of food safety standards.”), \ Ecobichon 2001 (“Pesticide use in developing countries.”);
    and Zidenberg-Cherr et al. 2000 (“Nutrition may influence toxicant susceptibility of children and elderly”) ↩︎

  26. Deziel et al. 2015, "A Review Of Nonoccupational Pathways For Pesticide Exposure In Women Living In Agricultural Areas" ↩︎

  27. Hertz-Picciotto et al. 2018 ↩︎

  28. FAO-STAT data, own visualisation, ‘top countries’ = importing >1,000 tonnes each year at least once ↩︎

  29. Donald et al. 2016 "Silicone Wristbands Detect Individuals' Pesticide Exposures In West Africa",
    Fuhrimann et al. 2022, "Pesticide Research On Environmental And Human Exposure And Risks In Sub-Saharan Africa: A Systematic Literature Review" ↩︎

  30. The report can be accessed here: https://panap.net/resource/of-rights-and-poisons-accountability-of-the-agrochemical-industry/?ind=1594041857622&filename=Of-Rights-and-Poisons-Accountability-of-the-Agrochemical-Industry.pdf&wpdmdl=2091&refresh=62945ed8c88531653890776 ↩︎

  31. Naksen et al. 2015, "Associations Of Maternal Organophosphate Pesticide Exposure And PON1 Activity With Birth Outcomes In SAWASDEE Birth Cohort, Thailand"
    Suwannakul et al. 2021, "Organophosphate Pesticide Exposures In Early And Late Pregnancy Influence Different Aspects Of Infant Developmental Performance" ↩︎

  32. Onchoi et al. 2020, “Organophosphates in meconium of newborn babies whose mothers resided in agricultural areas of Thailand” ↩︎

  33. Jaacks et al. 2019, "Association Of Prenatal Pesticide Exposures With Adverse Pregnancy Outcomes And Stunting In Rural Bangladesh" ↩︎

  34. Guo et al. 2019, "Associations Of Prenatal And Childhood Chlorpyrifos Exposure With Neurodevelopment Of 3-Year-Old Children" ↩︎

  35. Li et al. 2022, "Pesticide Exposure In New Zealand School-Aged Children: Urinary Concentrations Of Biomarkers And Assessment Of Determinants". ↩︎

  36. Xie et al. 2022, "Association Between Urinary Dialkylphosphate Metabolites And Dyslexia Among Children From Three Cities Of China: The READ Program"
    Scott & Pocock 2021, "The Health Impacts Of Hazardous Chemical Exposures Among Child Labourers In Low- And Middle-Income Countries" ↩︎

  37. Li & Kannan 2018, "Urinary Concentrations And Profiles Of Organophosphate And Pyrethroid Pesticide Metabolites And Phenoxyacid Herbicides In Populations In Eight Countries" ↩︎

  38. Thanks to Dr. Peter Morris for this suggestion, and Clare Donaldson for qualification. ↩︎

  39. Tarazona et al. 2022, "Improving The Risk Assessment Of Pesticides Through The Integration Of Human Biomonitoring And Food Monitoring Data: A Case Study For Chlorpyrifos" ↩︎

  40. Ein-Mor et al. 2018, "Decreasing Urinary Organophosphate Pesticide Metabolites Among Pregnant Women And Their Offspring In Jerusalem: Impact Of Regulatory Restrictions On Agricultural Organophosphate Pesticides Use?" ↩︎

  41. Wilson et al. 2010, "Exposures Of Preschool Children To Chlorpyrifos, Diazinon, Pentachlorophenol, And 2,4-Dichlorophenoxyacetic Acid Over 3 Years From 2003 To 2005: A Longitudinal Model"
    and Williams et al. 2008, "Changes In Pest Infestation Levels, Self-Reported Pesticide Use, And Permethrin Exposure During Pregnancy After The 2000–2001 U.S. Environmental Protection Agency Restriction Of Organophosphates" ↩︎

  42. Balalian et al. 2021, "Prenatal Exposure To Organophosphate And Pyrethroid Insecticides And The Herbicide 2,4-Dichlorophenoxyacetic Acid And Size At Birth In Urban Pregnant Women" ↩︎

  43. Figure 3 of Li et al. 2022, "Temporal Trends Of Exposure To Organochlorine Pesticides In The United States: A Population Study From 2005 To 2016"
    Ongoing detection of organochlorines is likely due to past use accumulating through food chains, rather than regulatory failure (Peng et al. 2020, "Exposure To Multiclass Pesticides Among Female Adult Population In Two Chinese Cities Revealed By Hair Analysis".) ↩︎

  44. Gunnell et al. 2017, "The Impact Of Pesticide Regulations On Suicide In Sri Lanka" ↩︎

  45. Weerasinghe et al. 2020, "Emerging Pesticides Responsible For Suicide In Rural Sri Lanka Following The 2008–2014 Pesticide Bans" ↩︎

  46. Both U.S. and E.U. figures are found in Grandjean & Bellanger 2017 ↩︎

  47. World Bank, 2022 https://data.worldbank.org/country/XO ↩︎

  48. Fuller et al. 2022, “Pollution and health: a progress update” ↩︎

  49. Fuller et al. 2022 ↩︎

  50. SDG Knowledge Hub, 2021, Accessed her: https://sdg.iisd.org/events/international-conference-on-chemicals-management-iccm5/ .
    This SAICM 2022 document says that dates for the conference will be considered in September 2022 - http://www.saicm.org/Portals/12/Documents/meetings/Bureau/ICCM5B20/SAICM_ICCM5-Bureau_TC_11_2_IP4%20and%20ICCM5%20Roadmap.pdf ↩︎

  51. SAICM, 2020 https://saicmknowledge.org/sites/default/files/meterial/SAICM_UCT%20HHP%20CoP%20Digest%20of%20the%20Global%20Action%20Plan%20%20Discussion%20DIGEST%2021%2010%202020%20doc.pdf ↩︎

  52. SAICM, 2021 http://www.saicm.org/Portals/12/Documents/meetings/Bureau/ICCM5B17/SAICM_ICCM5-Bureau_TC_9_5_%20Revised%20draft%20PoW%20and%20Budget%202021-2023.pdf , Fuller et al. 2022 ↩︎

  53. Fuller et al. 2022 ↩︎

  54. GEF page on chemicals https://www.thegef.org/what-we-do/topics/chemicals-and-waste , GEF project database on ‘pesticide’ (searches of ‘organophosphate’, ‘organophosphorous’, ‘chlorpyrifos’, and ‘parathion’ all return zero results) - https://www.thegef.org/projects-operations/database?project_search=pesticide.
    This impression of their focus is supported by detailed examination of their project on pesticide risk reduction in Bangladesh. Report available as the first project document here: https://www.thegef.org/projects-operations/projects/9076 Outcome 3.3, promotion of alternative, less-hazardous pest controls, could be interpreted to have some relevance to reducing organophosphates, but the connection is weak. ↩︎

  55. European Chemicals Agency (2022) report here: [https://echa.europa.eu/documents/10162/8a51d7d9-e9a4-2513-e975-492fb70f825c](https://echa.europa.eu/documents/10162/8a51d7d9-e9a4-2513-e975-492fb70f825c)
    Stockholm Convention consideration here: http://chm.pops.int/TheConvention/ThePOPs/ChemicalsProposedforListing/tabid/2510/Default.aspx ↩︎

  56. https://en.wikipedia.org/wiki/Fertilizer_and_Pesticide_Authority ↩︎

  57. Available here: https://fpa.da.gov.ph/NW/index.php/information-resources/publications/articles/305-fpa-proposes-php-346-7m-budget-during-da-s-internal-budget-session ↩︎

  58. UN 2022, “Synthesis Report on the Environmental and Health Impacts of Pesticides and Fertilizers and Ways to Minimize Them: Envisioning a Chemical-safe World” ↩︎

  59. UN 2022 ↩︎

  60. Fuller et al. 2022, Appendix ↩︎

  61. Causey et al. 2021, "Increasing The Impact Of Environmental Epidemiology In The Global Burden Of Disease Project" ↩︎

  62. Causey et al. 2021 ↩︎

  63. Available here: http://toxicslink.org/docs/Toxics%20Link%20-%20Annual%20Report%202018-19%20final.pdf ↩︎

  64. https://en.wikipedia.org/wiki/Pesticide_Action_Network , North America site here: https://www.panna.org/ ↩︎

  65. PAN-North America has total assets of ~$2.2M (https://www.panna.org/sites/default/files/PANNA-Audited-Fin-Stmts-3_31_20-and-19.pdf), PAN-Europe’s total budget was ~$311,000 (https://ec.europa.eu/transparencyregister/public/consultation/displaylobbyist.do?id=15913213485-46).
    PAN-Africa, PAN-Asia, PAN-Latin America all do not appear to have financial information available, but outward appearance and priors would suggest substantially lower budgets than PAN-North America and PAN-Europe. ↩︎

  66. https://centrepsp.org/country-work/# ↩︎

  67. https://www.givewell.org/research/incubation-grants/CPSP-general-support-jan-2021 ↩︎

  68. List made by selecting organophosphates as listed by Hertz-Picciotto et al. 2018 from PAN-International’s list of banned pesticides, last updated May 2022, available here: https://pan-international.org/pan-international-consolidated-list-of-banned-pesticides/ ↩︎

  69. Lee et al. 2021 The cost-effectiveness of banning highly hazardous pesticides to prevent suicides due to pesticide self-ingestion across 14 countries: an economic modelling study ↩︎

  70. Todd et al. 2020, "Gestational Exposures To Organophosphorus Insecticides: From Acute Poisoning To Developmental Neurotoxicity" ↩︎

  71. Costa et al. 2017, "Organophosphorus Compounds At 80: Some Old And New Issues" ↩︎

  72. Acephate - Liu et al. 2018
    Dimethoate - DeSesso 2008
    Fenitrothion - Ibrahim et al. 2020
    Malathion - Salama et al. 2015
    Naled - Silver et al. 2017
    Phosalone - Braquenier et al. 2007
    Phosmet - Vasamsetti et al. 2020
    Profenofos - Xu & Yang 2020
    Temephos - Laurentino et al. 2019 ↩︎

  73. Hertz-Picciotto et al. 2018 ↩︎

  74. List made by selecting organophosphates as listed by Hertz-Picciotto et al. 2018 from PAN-International’s list of banned pesticides, last updated May 2022, available here: https://pan-international.org/pan-international-consolidated-list-of-banned-pesticides/ ↩︎

  75. https://www.givewell.org/research/incubation-grants/CPSP-general-support-jan-2021 ↩︎

  76. SAICM, 2020 https://saicmknowledge.org/sites/default/files/meterial/SAICM_UCT%20HHP%20CoP%20Digest%20of%20the%20Global%20Action%20Plan%20%20Discussion%20DIGEST%2021%2010%202020%20doc.pdf ↩︎

  77. SAICM, 2020 https://saicmknowledge.org/sites/default/files/meterial/SAICM_UCT%20HHP%20CoP%20Digest%20of%20the%20Global%20Action%20Plan%20%20Discussion%20DIGEST%2021%2010%202020%20doc.pdf ↩︎

  78. Kongtip et al. 2013, "Organophosphate Urinary Metabolite Levels During Pregnancy, Delivery And Postpartum In Women Living In Agricultural Areas In Thailand" ↩︎

  79. Jaacks et al. 2019 ↩︎

  80. Boedecker et al. 2020, "The Global Distribution Of Acute Unintentional Pesticide Poisoning: Estimations Based On A Systematic Review" ↩︎

  81. Boedecker et al. 2020. ↩︎

  82. Grandjean & Landrigan 2014, "Neurobehavioural Effects Of Developmental Toxicity" ↩︎

  83. Sudakin & Stone 2011, "Dialkyl Phosphates As Biomarkers Of Organophosphates: The Current Divide Between Epidemiology And Clinical Toxicology" ↩︎

  84. Spaan et al. 2014, "Reliability Of Concentrations Of Organophosphate Pesticide Metabolites In Serial Urine Specimens From Pregnancy In The Generation R Study" although Hioki et al. 2019 suggests moderate reliability ("Intra-Individual Variations Of Organophosphate Pesticide Metabolite Concentrations In Repeatedly Collected Urine Samples From Pregnant Women In Japan") ↩︎

  85. Morgan et al. 2011, "The Reliability Of Using Urinary Biomarkers To Estimate Children's Exposures To Chlorpyrifos And Diazinon" ↩︎

  86. 0.9^6 ≈ 53% ↩︎

  87. GiveWell’s Pure Earth BOTEC is directly accessible here: https://docs.google.com/spreadsheets/d/1x0BchpoMphvAqSe71hJqM2gBByeRIf2oaz3WGVrVdow/edit#gid=1344390889
    It is contextualised in GiveWell (2021). The value comes from the effect of increased IQ on future earnings, and then converting future log increases in income to ‘units of value’. ↩︎

  88. See Michael Plant’s recent EA-Forum post offering a philosophical critique of how Open Philanthropy (and to some extent GiveWell) trade off between increasing income and improving health: https://forum.effectivealtruism.org/posts/bdiDW83SFAsoA4EeB/a-philosophical-review-of-open-philanthropy-s-cause ↩︎

  89. See Abreu-Vallaça & Levin 2017 for overview of the DNT potential of succeeding insecticide classes ("Developmental Neurotoxicity Of Succeeding Generations Of Insecticides") ↩︎

  90. Persson et al. 2022, "Outside The Safe Operating Space Of The Planetary Boundary For Novel Entities" ↩︎

  91. Persson et al. 2022 ↩︎

  92. Persson et al. 2022 ↩︎

  93. https://en.wikipedia.org/wiki/Registration,_Evaluation,_Authorisation_and_Restriction_of_Chemicals ↩︎

  94. Persson et al. 2022 ↩︎

  95. Mastorci et al. 2021, "Environment In Children’S Health: A New Challenge For Risk Assessment"
    Fuller et al. 2022,
    Grandjean & Landrigan, 2014 ↩︎

  96. Grandjean & Landrigan, 2014 ↩︎

  97. The fact that only half the set of neurotoxins have high volumes together with the fact that there are 2 new neurotoxins per year, implies that there is on average 1 new high-volume neurotoxin discovered each year.. ↩︎

  98. Gaylord et al. (2020) estimates the lost IQ points in the United States from four DNTs over 2001-2016, with an average of ~81.5M, or ~5M per year. We’ll take 1M IQ points/year as a conservative estimate for a novel DNT’s impact in the U.S.
    If we extrapolate to the world population (it’s not obvious whether the U.S. would be better or worse than the world average for DNT exposure), that suggests ~23.5M lost IQ points each year.
    We’ll use GiveWell’s conversion of 0.22 units of value per IQ point gained, and take 53% as the chance of there being a novel DNT detected in 30 years time. I assume a spend of $10M per year for 20 years to achieve the detection of a currently unknown DNT 10 years earlier:
    0.53 x 23.5M units of value x 0.22 x 10 years divided by 10M * 20 years = 0.137005 units of value per $
    = 137 units of value per $1000
    = ~40X the cost-effectiveness of GiveDirectly (3.4 units of value per $1000, as in GiveWell’s BOTECs) ↩︎

  99. Operational expenditure by REACH for 2021 was ~USD$10M - ECHA 2021: https://echa.europa.eu/documents/10162/8633921/FINAL_MB_59_2020_%282%29_Budget_2021_MB60-89ugl2u2.pdf/efb223e5-c459-f6e9-7a51-aef1c1c0583c ↩︎

  100. PCBs: first commercially manufactured 1930, banned in U.S. 1978.
    PBDEs: manufactured since 1960s, first bans in 2003 and international ban in 2009
    Tetrachloroethylene: first synthesised 1821, commercially manufactured since 1910, identified as DNT in 2013 but not in 2006
    Chlorpyrifos: patented in 1966, voluntary restrictions ~2000, bans beginning 2008 ↩︎

  101. Operational expenditure by REACH for 2021 was ~USD$10M - https://echa.europa.eu/documents/10162/8633921/FINAL_MB_59_2020_%282%29_Budget_2021_MB60-89ugl2u2.pdf/efb223e5-c459-f6e9-7a51-aef1c1c0583c
    The other large testing body might be the EPA. Before REACH, there was seemingly no comprehensive process, so I expect expenditure to be significantly lower. ↩︎

  102. Krewski et al. 2020, “Toxicity Testing In The 21St Century: Progress In The Past Decade And Future Perspectives"
    National Research Council, 2007, “Toxicity testing in the 21st century: a vision and a strategy.” ↩︎

  103. Barr et al. 2021, "The Use Of Dried Blood Spots For Characterizing Children's Exposure To Organic Environmental Chemicals"
    Zare Jeddi et al. 2021, "Towards A Systematic Use Of Effect Biomarkers In Population And Occupational Biomonitoring" ↩︎

  104. Grandjean & Bellanger (2017) summarise the cognitive deficits due to methylmercury as costing the U.S. $4.8B and the E.U. $10.8B.
    Zhang et al. (2021) suggest a global annual cost of $117B from mercury exposure, and model the 2010-2050 costs are ~$19T ( "Global Health Effects Of Future Atmospheric Mercury Emissions")
    Basu et al. (2018) gives a good summary of exposures in different populations ("A State-Of-The-Science Review Of Mercury Biomarkers In Human Populations Worldwide Between 2000 And 2018"). ↩︎

  105. Global Environment Facility on mercury: https://www.thegef.org/what-we-do/topics/mercury
    Pure Earth on mercury: https://www.pureearth.org/our-projects/global-mercury-program/ Also some work by IPEN: https://ipen.org/tags/mercury
    Readers interested in looking into mercury further can see my very rough notes here, as I went down the mercury rabbit hole an embarrassingly long time before bothering to check what work was already being done. ↩︎

  106. Gaylord et al. (2020) estimates that for the U.S. 2001-2016 the cognitive losses due to PBDEs are even higher than lead, which is saying something. Grandjean & Bellanger (2017) include analysis of PBDEs, but estimates for LMICs are lacking. I don’t know much more about PBDEs other than their being banned under the Stockholm Convention - so looking into exposure pathways and burdens in LMICs and considering possible interventions is an open research question. ↩︎ ↩︎

108

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11 comments, sorted by Click to highlight new comments since: Today at 6:35 AM

Hi Ben, congratulations on winning! Fantastic post!

I'm based in Tanzania, and have connections to the ministry  of agriculture (can get this in front of the minister pretty easily if we have a good case for how large an issue it is in Tz). How would you recommend trying to find out how big an issue this might be here?

Hi Arno, thanks! That's a really good question. I'll say upfront that I'll be following-up with Open Phil over the coming weeks, and may have a better idea of what next steps look like then. Here's my initial stab.

I think there's three complementary approaches: 1) indirect public data/literature, 2) indirect government data, and 3) direct measurements.

  1. I had a brief look at Google Scholar and there's some interesting pieces of indirect evidence suggesting OP exposure might be a problem in Tanzania (I may be able to look into this in greater depth in the next few weeks):
    - Calista et al. (2022) appears to be an excellent and very recent source on the health effects of pesticide exposure in Tanzania, and identifies organophosphates as a concern. 
    - Boedecker et al.'s (2020) systematic review of acute unintentional pesticide poisonings suggest severely high incidence in Tanzania with 76.35% of farmers experiencing it (among the highest results in all countries considered). Thailand, which was my reference for direct measurements of OP metabolites in the urine of pregnant women, had an incidence of 36%
    - Mwevura et al. (2021) find organophosphate residues exceeding safety guidelines in soil, water, and sediment in the Rufiji River Delta in Tanzania
    - Bardner & Mcharo (2008) find that a moth species called L. meyricki, which is a pest for coffee crops, has developed general resistance to organophosphates in northern Tanzania. It appears a lot of other papers have been written about this, especially with respect to mosquito resistance as OPs have been used as vector control, e.g. mosquitoes, bedbugs. I think this is a tricky area. It might be hard to disentangle analysis of OPs used for farming vs. for vector control, and the use-practices, exposures, and cost-benefit analyses will differ. I didn't look at vector control in depth in my article, partly because the benefits seem stronger and justifying regulation seems more difficult.
    - Ngowi (2002; dissertation) finds that most pestcides used in Tanzania are organophosphates. This dissertation is long but appears thorough and very relevant, although it is quite old. 
    - Lekei et al. (2020) find that acute pesticide poisoning is common among women in Tanzania, and that organophosphates are the most important and most common type used. 
    - Lekei et al. (2014) find that organophosphates are the second most common class of pesticide used in Tanzania
    - Lekei et al. (2014b) assessed farmer's knowledge, practices, and experiences of exposure and found concerns, including widespread storage of pesticides in the home. This is also found by Manyilizu et al (2017).
    - Kapeleka (2020; thesis) found vegetables were highly contaminated with organophosphates in Tanzania.
    - Wylie et al. (2017) looked at  urinary OP metabolites in 17 pregnant women in rural Ghana, which has a lower incidence of acute unintentional pesticide poisoning according to Boedecker et al.  They found widespread exposure for  specific OP metabolites with higher levels than non-pregnant U.S. cohort - but strangely, quite low levels for non-specific metabolites (they put this down to field conditions?)
     
  2. FAO-STAT data is pretty coarse, but broadly suggests Tanzania is importing less hazardous pesticides over time (note however that many OP pesticides are not classified as highly hazardous). If you were collaborating with the government I would imagine that they may have much better data on import quantities and potentially usage of organophosphates specifically. 
     
  3. Much of the above is quite indirect. Ideally we would have good, large-sample, representative data showing levels of exposure in pregnant women in Tanzania. So far I haven't seen such a study, although I think there were some of pesticide workers in the 1990s/early 2000s. This might suggest a natural next step - fund/organise a pilot study of urinary DAPs (or other measures) in Tanzanian pregnant women from several representative communities. As well as providing direct information to guide current action, it could also serve as the beginning of a longitudinal study to  investigate the existence of a DNT effect in this context. Elikana Lekei is a Tanzanian academic whose name keeps coming up who might know a lot about this .

I hope that helps! As I said, I'll have a better idea in coming weeks of how Open Phil might want to proceed, if indeed they do. My impression of briefly looking at the literature suggests the indirect evidence for OPs being a problem in Tanzania is strong, but there's a lot more work to consider agricultural impact, regulatory environment,  pesticide alternatives, etc, as well as considering the value of getting direct evidence. I also don't know when and how approaches to government should be made, if indeed they should - but I hope others' input will clarify things in the coming months. 

Thanks for your interest and great question!

Nice one, thanks Ben! Will dig into these a bit!

I agree, that before trying to get them kaiboshed completely it would be very good to understand what that looks like for the ag space and what the alternatives are and how cost effective are they? From my knowledge of pesticide usage in Tz and SSA, there are definitely alternatives that exist in the market which are being used already to reasonable effect which indicates the alternatives are comparable on a price to efficacy level (smallholders wouldn't spend money on these things if they don't see some results). 

Let me know how you're moving forward on this, would be happy to chip in/help where possible as I think there's some low hanging fruit that can be gotten based on my experience of the regulatory environment. Can get me on whatsapp +255763998637

Cheers!

Congrats. This is great.
I just found out that LMICs (at least Brazil) import pesticides from countries where such products are banned. Thus advocacy in HIC could target exports, too, since it is often more effective than advocacy in LMICs - e.g., Germany is currently pushing for a ban of such exports in EEUU, while in my home state, norms that forbade importing a pesticide from countries where it is banned have been repealed.

I'm very honoured that this won! Because I expect an uptick in readers for the next few days, I wanted to share an important critique that I didn't have time to incorporate properly. Tony Senanayake was overall supportive of this paper, but he was also very kind to provide these counterpoints, and to grant me permission to replicate them here:

General issue that I have: Economic empowerment is incredibly valuable to those in LMIC. This has been observed time and again by the revealed preferences of ‘beneficiaries’ in these countries. For example, we see people in India actively harming their health by moving to highly-polluted cities in India (like Delhi) in search of economic opportunities. The use of low-cost, validated, insecticides has the ability to increase yields, income and economic opportunities for farmers. These farmers often make up the plurality if not majority of the citizens in LMIC and generally are a large majority of those living in poverty in these countries. You do note that the impact on yield and livelihoods is an important component of a fuller analysis, however, I think it is something that is critical to highlight more even in this short analysis. Cause prioritization requires a fair trade-off between competing interests and if those we are looking to serve have voted by their feet that they tend to prioritize economic empowerment over health we should value that in some way. I would argue that a discounting in the BOTEC would help here. Furthermore, you may want to include in your questions the need to survey / speak with potential beneficiaries to understand their preferences as they weigh up economic empowerment and health. 

Outcome Measurement: The majority of the research you cite and the BOTEC assumptions are focused on IQ outcomes. In the development economic literature in the education space we tend to focus on student learning outcomes as measured by quality and quantity of education. The two measures that are now used as standard measures are Equivalent Years of Schooling and Learning Adjusted Years of Schooling. I would recommend adding some wording that links the IQ outcomes to EYOS or LAYS and then to measures of wellbeing (such as DALYs / QALYs / income etc). This would complete the Theory of Change that you set out. At the moment, the analysis only works through a part of the Theory of Change and leaves the reader assuming that an increase in IQ leads to welfare gains. This is a fair assumption, but not a validated one. 

Sri Lanka case study: This is a personal point for me as my family is Sri Lankan. The Sri Lankan case study is a very troublesome one. You are right that the government outlawed insecticides and pesticides and moved to ‘green agriculture’. However this is move is also seen as one of the major contributing factors to the decline in agriculture yields which precipitated the food shortages and economic crisis we are now seeing in Sri Lanka. If you are going to use Sri Lanka as an example, I think it is important to recognize these secondary consequences of policies. The unintended consequences of policies are often large and by definition uncertain and can outweigh the expected benefits.

This is a great piece - and a worthy winner of the prize.

I have some concerns about tractability. I can easily see how lobbying in LMICs could lead to regulation banning pesticides etc. This would be cheap to try, and seems obviously worth investigating and researching to develop a proposal.

But banning XYZ this will not necessarily solve the problem - because we know that the state's capacity to enforce regulation is weak in many of these contexts. There already exist laws on other forms of pollution which are not enforced in practice.

Against that - consider case of Bangladesh and banning lead in petrol. Basically an overnight success. http://web.worldbank.org/archive/website00811/WEB/OTHER/E8864F3B.HTM?OpenDocument#:~:text=According to Bangladesh Petroleum Corporation,is now free of lead.

My guess would be that if there are pesticides etc. that can be replaced by less damaging alternatives, with little to no loss in yield/performance - then this could be easily tractable. But that it isn't going to be very tractable if it requires small-scale farmers to make financial sacrifices.

I broadly agree - I think for any realistic analysis of this area, the question isn't whether regulation completely solves the problem, but what relative reduction is achievable. I tried to model this in the BOTEC by being fairly conservative about the decrease in exposure:

However, these inputs are also accounting for the probability of success of passing regulation at all - so it's reasonable to think these estimates should be even more conservative. 

This is action-guiding too - selecting which countries to work in would need to consider the domestic regulatory environment  and what the supply chain looks like in that context.

And I think your point is supported by my impression of the experiences of the Lead Exposure Elimination Project. Their impact in Malawi, their first target country, wasn't through passing a law, but in getting pre-existing standards enforced and monitored. If any org was pursue organophosphates as a cause area in the future, I think assisting monitoring and compliance would be an important component. 

Another worry I have is about interpersonal aggregation, which I didn't capture in the post. The 'importance' of this cause area depends on a large number of fairly mild harms (slight decrease in IQ, slight decrease in earnings, slight decrease in welfare). The large number of people affected suggests the overall magnitude is large, but I feel uncertain and queasy about suggesting it is more important than a much smaller number of serious harms (e.g. a debilitating disease or premature death).

I was so excited to see the title of this winning cause proposal! 

And then I was so surprised to see that the reasoning focused on the concern that pesticides may, unintentionally, harm people

I love the idea of fighting pesticide use! And I love it for a totally different reason:

It seems to me that fighting pesticides could help quadrillions of insects and other animals. 

While I'm not a scientist, it seems to me that insects probably have feelings. I'm getting this idea from three things:  (1) First, the insect-related pop-sci news articles I've read (e.g. this). (2) Second, simply observing insects,  and seeing how they sometimes seem scared of me and try to evade me, the same way other animals do.  (3 ) And third, hypothesizing, without evidence, that perhaps we animals developed sentience around the same time as we developed the ability to move, as a way to get away from harmful stimuli.  And insects can move.

Even if someone doesn't agree with me that insects probably have feelings, I think most reasonable people would have to admit that there's some chance that insects might have feelings. Like let's say a 10% chance.  Google says there are  10 quintillion insects alive. So even a 10% chance of insects having feelings is, in a sense, morally equivalent to 1 quintillion beings who we know for sure have feelings. That would mean we should care a lot about insects' feelings. Even if insects are somehow less sentient than other animals, 1 quintillion half-sentient beings is still the moral equivalent of half-a-quintillion totally-sentient beings. 

I realize the things I'm saying are  counterintuitive. They feel counterintuitive to me, too, even though I'm the one saying them. And I understand why people are more passionate about helping larger animals, like people. I'll admit that I don't do much in my life to protect insects. And I have killed huge numbers of insects in my life. But  I think it would be nice if we could try to treat insects a little better.

I would assume pesticides cause immense suffering to the animals they're designed to kill. So, even if only a fraction of insects are harmed by pesticides, we could probably do a huge amount of good by reducing pesticide use! 🐞

Plus, pesticides harm multiple types of animal species, not just insects and humans, right?

Anyway, kudos to Ben and OP! Down with pesticides!

Thanks alene! These are interesting points and are important to think about. I agree there's a decent chance that insects are sentient (maybe 0.1 to 20% range with extreme uncertainty, and variance depending on which specific species we are talking about). The best source I know on this is Rethink Priorities' report, with exhaustive results here, and the bottom line opinion of each author summarised here. The number of insects and potential for suffering is gravely concerning.

However, I don't think that justifies a complete opposition to pesticide use. Pesticides are extremely useful and valuable for feeding more humans and reducing the amount of land needed for crops. Washuck et al. (2022) analysed studies of pesticide use in the U.S. and Canada 2015-2019. They calculated that pesticides preserved millions of hectares of habitats and fed millions more humans (table below).

But there's a deep discussion about ecology, climate change, food systems, agriculture, wild animal welfare and much else that besides that complicates the above; I really don't know. 

As well as  the large benefits of pesticides, the other reason I would tentatively oppose a blanket ban is tractability. Regulating organophosphates is already difficult; trying to ban all pesticides would be extremely difficult politically, with profound opposition by industry and agriculture. Especially if the main benefits of such a ban were based on insect suffering.

I think there's a middle way though, following the lead of the wild animal welfare ideas I've heard. That idea would be to try to guide farmers/governments/industry to pesticides that cause less suffering as they move away from organophosphates. I would need to read and think a lot more about this to figure out my own views, but this report by the Wild Animal Initiative looks promising. Interestingly, they note a possibility that organophosphates are a (relatively) more humane class because they are faster acting. Non-pesticide based methods may be most promising.  It appears  unclear and complex though.

I'm not sure of the promise of trying to guide farmers to more humane alternatives - at face value that seems a more difficult outcome to reliably achieve than bans/de-registrations. But if work on organophosphates or pesticide-suicide prevention built networks to influence pesticide policy in LMICs, that may be a resource to layer in insect welfare efforts in the future.

Anyway, interesting comment!